FÍSICA Y QUÍMICA 3º DE E.S.O.

1. FÍSICA Y QUÍMICA3º DE E.S.O. UNIT 1: THE ATOMIC STRUCTURE OF MATTER FQ3ESO_U1_1: ATOMIC MODELS U.1_1 d1

2. Bloque 2. La materia 2.7. Estructura atómica. Isótopos. Modelos atómicos.. Criterios de evaluación C.E.2.6. Reconocer quelosmodelos atómicos son instrumentos interpretativos de las distintas teorías y lanecesidad desu utilización parala comprensión delaestructura interna dela materia. CMCT, CAA. Estándares de aprendizaje evaluables EE.A.2.6.1. Representa el átomo, a partir del número atómico y el número másico, utilizando el modelo planetario. E.A.2.6.2. Describe las características de las partículas subatómicas básicas y su localización en el átomo. E.A.2.6.3. Relaciona la notación AZX con el número atómico, el número másico determinando el número de cada uno de los tipos de partículas subatómicas básicas. Criterios de evaluación C.E.2.7. Analizar la utilidad científica y tecnológica de los isótopos radiactivos. CCL, CAA, CSC Estándares de aprendizaje evaluables E.A.2.7.1. Explica en qué consiste un isótopo y comenta aplicaciones de los isótopos radiactivos, la problemática de los residuos originados y las soluciones para la gestión de los mismos. U.1_1 d2

3. 0.- PRECEDENTS OF THE ATOMIC MODELS U.1_1 d3

4. 0.- PRECEDENTS OF THE ATOMIC MODELS Democritus Siglo V a.C. Around 400 B.C., a Greek philosopher named Democritus came up with the idea that atoms make up all substances “By convention sweet, by convention bitter, by convention hot, by convention cold, by convention colour: but in reality atoms and void ” Demócrito por Antoine Coypel (1692). U.1_1 d4

5. 1.- FUNDAMENTAL LAWS OF CHEMISTRY In the eighteenth and nineteenth centuries, chemical reactions were studied. Some regularities were found. As a result, the first atomic model of matter could be established (The atomic theory of Dalton) LAVOISIER LAW OR LAW OF CONSERVATION OF MASS: In any chemical reaction the total mass of the substances that will react is equal to the total mass of products. The mass is kept constant in a chemical reaction. U.1_1 d5

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9. 1.- FUNDAMENTAL LAWS OF CHEMISTRY U.1_1 d9

10. 1.- FUNDAMENTAL LAWS OF CHEMISTRY U.1_1 d10

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12. 1.- FUNDAMENTAL LAWS OF CHEMISTRY LEY DE PROUST O LEY DE LAS PROPORCIONES DEFINIDAS: Cuando dos elementos reaccionan para dar un compuesto siempre lo hacen en una proporción constante en masa. En todos los casos el cociente entre la cantidad de hidrógeno y oxígeno que reacciona es constante U.1_1 d12

13. 2.- THE ATOMIC THEORY OF DALTON John Dalton 1805 To explain these experimental laws , John Dalton, thinks of a model of the atom as a solid sphere. He proposed the first atomic theory. U.1_1 d13

14. 2.- THE ATOMIC THEORY OF DALTON John Dalton 1805 a) Matter is made of tiny indivisible particles called atoms U.1_1 d14

15. 2.- THE ATOMIC THEORY OF DALTON John Dalton b) There are different kinds of atoms with different masses and properties. Atoms of an element are all equal and have the same properties. By contrast, the atoms of different elements are different and have different properties. c) Atoms are indestructible and unchangeable (They cannot be transformed from one type to another) U.1_1 d15

16. 2.- THE ATOMIC THEORY OF DALTON John Dalton 1805 d) The chemical compounds are formed by the union of an integer number of atoms of different elements, always in the same proportion. U.1_1 d16

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18. 2.- THE ATOMIC THEORY OF DALTON John Dalton 1805 e) In chemical reactions of substances, atoms are separated, combined and redistributed among reactive substances. However, no atom is created, or destroyed, or becomes an atom of another element. U.1_1 d18

19. 2.- THE ATOMIC THEORY OF DALTON John Dalton The atomic theory should be considered as one of the most important pillars of modern chemistry 1805 A set of scientific facts would reveal significant gaps and errors in the atomic theory: - The electrical nature of matter, - The internal structure of the atom, - The existence of isotopes, - Radioactivity - Etc.). U.1_1 d19

20. 3. THE INTERNAL STRUCTURE OF THE ATOMS 3.1. THOMSON DISCOVERED THE ELECTRON Thomson discovered the electron in 1897 Cathodic rays tube U.1_1 d20

21. 3. THE INTERNAL STRUCTURE OF THE ATOMS 3.1. THOMSON DISCOVERED THE ELECTRON William Crookes He invented the Crookes tube, which was used to study the properties of the so-called "cathode rays". (Now it is known to be a stream of electrons) The discharges tubes are glass ampoules with metal disks that work as electrodes. Inside the tube the gas is evacuated. U.1_1 d21

22. 3. THE INTERNAL STRUCTURE OF THE ATOMS 3.1. THOMSON DISCOVERED THE ELECTRON William Crookes In 1875 he discovered that by applying a high voltage between the electrodes a luminescence appeared in the anode side. https://www.youtube.com/watch?v=Xt7ZWEDZ_GI U.1_1 d22

23. 3. THE INTERNAL STRUCTURE OF THE ATOMS 3.1. THOMSON DISCOVERED THE ELECTRON William Crookes Grinders with blades were introduced inside the tubes and found to be set in motion Conclusion: cathode rays were composed of particles U.1_1 d23

24. 3. THE INTERNAL STRUCTURE OF THE ATOMS 3.1. THOMSON DISCOVERED THE ELECTRON Joseph J. Thomson 1904 Thomson changed the tubes including two parallel plates, one positively charged and one negatively charged. The rays were diverted to the positive plate Conclusion: Cathode rays are negatively charged http://www.dnatube.com/video/7118/Cathode-ray-tube See it live!!! U.1_1 d24

25. 3. THE INTERNAL STRUCTURE OF THE ATOMS 3.2. X RAYS AND RADIACTIVITY Scientists thought that the radioactive emissions should come from a very internal area inside the atom. So the atom should be more complex than that proposed by Dalton U.1_1 d250

26. 1. LOS PRIMEROS MODELOS ATÓMICOS 1.1. MODELO ATÓMICO DE THOMSON 1904 Thomson decided from his experiments that atoms contained small, negatively charged particles. He thought these “electrons” were spread out evenly throughout a positively charged sphere. His model, shown in the figure below, looks like a ball of chocolate chip cookie dough. “The Plum Pudding Model ” U.1_1 d26

27. Ernest Rutherford 1911 The planetary model of atom Rutherford experiment : He bombarded a gold sheath with alpha particles U.1_1 d27

28. 1. LOS PRIMEROS MODELOS ATÓMICOS 1.2. MODELO ATÓMICO DE RUTHERFORD 1911 The planetary model of atom Just as Rutherford himself said: « "It was quite the most incredible event that ever happened to me in my life. It was almost as incredible as if you had fired a 15-inch shell at a piece of tissue paper and it came back and hit you."»  Rutherford: propone el modelo nuclear del átomo U.1_1 d28

29. Ernest Rutherford The planetary model of atom Rutherford, thought that almost all the mass of an atom and all its positive charge were concentrated in the nucleus of an atom. He also thought the nucleus of an atom was surrounded by electrons U.1_1 d29

30. Ernest Rutherford 1911 The planetary model of atom U.1_1 d30

31. Ernest Rutherford 1911 But there was a problem… U.1_1 d31

32. Niels Bohr When white light is passed through a prism (as shown in the figure above), bands of bright light with different colours are observed against a black background. And another problem… U.1_1 d32

33. Niels Bohr Why? Emission Spectrum of Hydrogen When an electric current is passed through a glass tube that contains hydrogen gas at low pressure the tube gives off blue light. When this light is passed through a prism (as shown in the figure above), four narrow bands of bright light are observed against a black background. https://www.youtube.com/watch?v=OJzW2RoZq1Y U.1_1 d33

34. Niels Bohr 1913 Danish physicist named Neils Bohr hypothesized that electrons travel in fixed orbits around the nucleus of the atom, as the figure below shows. Bohr proposed the orbit of the electron is fixed at stable energy levels Orbits are quantized U.1_1 d34

35. Niels Bohr The quantic model 1913 An electron changes orbits in a sudden quantum leap. When the atom absorbs electromagnetic radiation or photon (2) the electron (1) changes from an inner orbit to an outer one (3). The energy difference between the initial and final orbits is the same as the absorbed energy http://www.youtube.com/watch?v=dYoO5YWLd7k When the electron returns (4), the energy difference between the outer and inner orbits is emitted by the atom in the form of electromagnetic radiation or photon (5). http://www.youtube.com/watch?v=aRLAYJGmpwQ U.1_1 d35

36. Niels Bohr 1913 U.1_1 d36

37. Niels Bohr When the electrons return to inner orbits, the energy difference between the outer and inner orbits is emitted by the atom in the form of electromagnetic radiation or photons. When this light is passed through a prism, bands of bright light are observed against a black background. U.1_1 d37

38. Oxygen spectrum Neon spectrum Na K Li Ba Hg He H Examples of Spectra https://www.youtube.com/watch?v=QI50GBUJ48s U.1_1 d38

39. Absorption Spectra The absorption spectrum is produced when a transparent and relatively cool gas absorbs part of the light in the continuous spectrum of a hotter source. It appears as a series of black lines superimposed on the continuous spectrum, with the black lines corresponding to the absorbed energies U.1_1 d39

40. Emission vs. Absorption Spectra Spectra of Mercury U.1_1 d40

41. Bright-line spectra U.1_1 d41

42. Bright-line spectra U.1_1 d42

43. Bright-line spectra U.1_1 d43

44. One of Bohr’s students, James Chadwick, found that the nucleus not only contained positive protons but also neutral neutrons U.1_1 d44

45. The wave-mechanical or quantum-mechantical model By 1926, scientists had developed the electron cloud model of the atom in use today Electrons move so fast and have so little mass that it is impossible to know where the electrons are. It is best to describe their location as somewhere in a “cloud” or zone called orbital U.1_1 d45

46. The wave-mechanical or quantum-mechantical model Orbitals and quarks U.1_1 d46

47. Inside the heart of an atom? U.1_1 d47